1. Field of the Invention
The present invention relates to a recording medium (or recording paper) for recording with ink, particularly to a recording medium superior in ink color developing properties and capable of forming a water-resistant recorded image with high resolution. The present invention also relates to a recording method using the recording medium.
2. Related Background Art
Recording mediums for ink jet recording hitherto known are: (1) those of low-sized paper made from pulp as the main constituent, in a form like filter paper and blotting paper; (2) those constituted of base paper exhibiting low ink absorbency, and an ink-receiving layer provided thereon by use of porous inorganic pigment; and the like.
On the other hand, in ink jet recording for forming color images of high quality with high resolution, recording mediums to be employed are required to satisfy the requisites as below:
(1) Satisfactory color development of ink applied to the recording medium, PA1 (2) Substantially complete circularity of an ink dot, PA1 (3) Sufficient ink absorbing capacity for preventing ink from flowing out even when a plurality of ink droplets are attached to the same spot, PA1 (4) Sufficient ink fixing property to prevent running of ink even when an ink droplet is rubbed immediately after application of ink to the recording medium, PA1 (5) Satisfactory preserving property for formed images, such as water-resistance and light-fastness. PA1 .eta.: Viscosity coefficient of liquid PA1 .lambda.: Electroconductivity of liquid PA1 .epsilon.: Dielectric constant of liquid PA1 C.I. Direct Black 17, 19, 32, 51, 71, 108, and 146, PA1 C.I. Direct Blue 6, 22, 25, 71, 86, 90, 106, and 199, PA1 C.I. Direct Red 1, 4, 17, 28, and 83, PA1 C.I. Direct Yellow 12, 24, 26, 86, 98, and 142, PA1 C.I. Direct Orange 34, 39, 44, 46, and 60, PA1 C.I. Direct Violet 47, and 48, PA1 C.I. Direct Brown 109; and C.I. Direct Green 59; PA1 C.I. Acid Black 2, 7, 24, 26, 31, 52, 63, 112, and 118, PA1 C.I. Acid Blue 9, 22, 40, 59, 93, 102, 104, 113, 117, 120, 167, 229, and 234, PA1 C.I. Acid Red 1, 6, 32, 37, 51, 52, 80, 85, 87, 92, 94, 115, 180, 256, 317, and 315, PA1 C.I. Acid Yellow 11, 17, 23, 25, 29, 42, 61, and 71, PA1 C.I. Orange 7, and 19, PA1 C.I. Acid Violet 49, and the like; and PA1 C.I. Food Black 1, and 2.
No recording medium, however, has been known which satisfies all the requisites mentioned above.
In particular, in ink jet recording, since it uses aqueous ink, there are posed problems that the recorded image has low water-resistance, and thus that decipherment of the image becomes very difficult because of blurring of ink when the image is wetted with water. These problems are required to be solved.
The ink-jet recording paper disclosed in Japanese Patent Application Laid-open No. 56-99693 (1981), for. example, employs quaternary ammonium halide to improve water-resistance. Such water-resistant ink-jet recording paper involves the disadvantage of remarkable decrease of light-fastness of a recording agent (e.g., dyes).
Water-resistance improving agents for image, having specified constitutions, are disclosed in Japanese Patent Application Laid-open Nos. 56-84992, 59-20696, 59-33176, and 61-58788. Each of these water-resistance improving agents has a primary, secondary or tertiary amino group, or a quaternary ammonium group, so that the light-fastness of the ink-jet-recorded images is not sufficient even though water resistance is sufficient.
Since dyes used in ink-jet recording are anionic in the prior art, an amine type compound is incorporated as a water-resistance improving agent into an ink-jet recording medium. However, the addition of such an amine type compound lowers disadvantageously light-fastness of images, and even with various improvements, lowering or decrease of the light-fastness cannot be avoided.
An example of a recording medium employing a water-resistance improving agent other than amine type compounds is disclosed in Japanese Patent Application Laid-open No. 60-257286. In this disclosure, a basic polyaluminum hydroxide compound is used as a water-resistance improving agent. According to the knowledge of the inventors, the compound shown in the Japanese Patent Application Laid-open No. 60-257286 is a water-soluble polycationic compound, which is not sufficient for imparting water-resistance to a recording medium where a large quantity of dye is incorporated into a recording medium to give an image in high definition and high concentration.
As mentioned above, no satisfactory measure has been found for achieving simultaneously water-resistance and light-fastness of an ink-jet-recorded image.